In some packaging and filling systems of paper-made containers filled with liquid food such as juice and milk, final shapes of the containers are obtained by forming web-like packaging laminated materials having predetermined folding lines in tubular shape, lapping both ends of the packaging material and forming overlap, longitudinally sealing in the longitudinal direction of the tube by the overlap, filling food into the tubular packaging material, pressing the tubular packaging material in the predetermined intervals to seal the material by transversal seal in transversal direction, cutting at the center of the transversal seal zone to obtain a pillow-like preliminary forming, and sealing flaps containing the transversal seal zone formed by folding along the folding lines to side wall of the container and bottom face of the container.
FIG. 1 shows an outline of one example of a filling packaging machine for the paper-made container. The filling machine shown in this example winds out a packaging material web 1 having thermoplastic material layer on the inner and outer layers, wound in roll shape, transfers it in the filling machine by rollers, bonds a trip tape 2 to one end of the packaging material web by a strip tape applicator 3, passes the packaging material web in a sterilizing bath 4 and sterilizes, removes the sterilizing agent by an air knife 5, forms the tubular packaging material by a forming roller 6, forms an overlap by lapping both ends of the packaging material, longitudinally seals the overlap in the tube longitudinal direction by a longitudinal seal element 8 to form a longitudinal seal zone, fills liquid food into the tube from a filling pipe 7, sandwiching this tube by a sealing jaw 10 and an oppositely arranged jaw 11 while sending this tube downward by a length equivalent to one packaging container, forms two transversal seal zones by transversally sealing in the crossing direction, at the same time continuously forms pillow-like preliminary forming 12, cuts middle of the seal zone of the connected pillow-like preliminary forming by knife or the like to separate to individual pillow-like preliminary forming 13, bends flaps on the upper and lower of the separated pillow-like preliminary forming at a final folder 15 to form a finally shaped packaging filling container 14.
FIG. 2 shows an aspect in which the pillow-like preliminary forming 13 is folded at the final folder 15. The pillow-like preliminary forming 13 is sealed by two transversal (transversal line) seal zone 23 and longitudinal seal zone 26. The pillow-like preliminary forming 13 has side walls 22, 22zone 22a defined by the folding lines (refer to FIG. 2(a)). As shown in FIG. 2(b), the main body of the pillow-like preliminary forming is formed in rectangular solid along the folding lines. On the edge, the transversal seal zone 23 and flaps 24, 25 are formed to be upright from the container wall. The transversal seal zone 23 is upright from the bottom face 22zone the top face 22a. The flaps 24 and 25 integrally communicate with the container wall through ridge sides 25a and 24a. Next, as shown in FIG. 2(c), after the transversal seal zone 23 is folded, the flaps are rotated around the ridge side as a center, a container top side flap 24 is folded into the side wall 22, and the container bottom side flap 25 is folded into the bottom face 22b. FIG. 3 shows perspective views of outline of a rectangular solid liquid food filling paper-made container (FIG. 3(a)) according to the folded aspect shown in FIG. 2, and a liquid food filling paper-made container (FlG. 3(b)) whose main body center is octangular column according to a similar aspect. The containers 14 have a folded transversal seal zone 23, container walls 22 and 22a and a longitudinal seal zone 26 running to the bottom face from the top wall 22a through the container wall on the back, and is provided with the flap 24 folded through the ridge side 24a. Each container has a straw penetrating sealing hole 33, a faucet 32 and a sealing pull-tab 31.
Sufficient sealing must be carried out at said seal zone so as to prevent the liquid food contained in the container from leaking and being exposed to external air. However, if the temperature and pressure on the transversal seal are improper, the melted thermoplastic material on the packaging laminated material may protrude into the container into which the content is filled. The melting substance directly contacts the contained liquid foods, and becomes brittle by sharply cooling, and the laminated material may be broken from the protruded location. For sealing, it is necessary to obtain a transversal seal whose melted substance does not protrude into the container. In addition, for forming, stress may be concentrated on the formed portion or folded portion, thereby causing damages such as pinhole and crack. And further, damage of sealing defect may be caused. Then, liquid food containers commercialized by the filling packaging machine are regularly and individually sampled by the operator of the machine for inspection, and the sampled container, whose flap is peeled, is deformed to pillow-like shape from rectangular solid shape, and then inspected for seal strength, presence or absence of pinhole, and further overlap width of the longitudinal seal depending on empirical procedure of the operator.